Mold material processing device, method and apparatus for producing same

ABSTRACT

The invention relates to a molten material processing device having an elongated thermal element like a heating element, a thermocouple, a sensor, a heatpipe and a cooling pipe which is characterized in that the elongated thermal element is located in a recess provided in a surface of the molten material processing device, the recess, including a first portion and a second portion, has a cross-section which is larger than a cross-section of the thermal element, so as to provide a clear space between the thermal element and the surface of the processing device, the clear space which is limited by the first portion and the thermal element is filled by a thermally sprayed material and the second portion, which is adapted to the cross-section of the thermal element, partially surrounds and directly contacts same.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.10/276,962, which was the National Stage of International ApplicationNo. PCT/IB01/01710, filed May 25, 2001, the contents of which areincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a molten material processing devicehaving an elongated thermal element, such as a heating element, athermocouple, a sensor, a heatpipe and/or a cooling pipe. The inventionrelates further to a method and an apparatus for producing the moltenmaterial processing device.

Such a molten material processing device is known from U.S. Pat. No.5,051,086.

Thermal elements, for example heating elements, are used in the moltenmaterial processing device so as to provide the heat required to raisethe temperature in the processing device to a process temperature and tomaintain the temperature.

Because of the short cycle times to be realized in modern injectionmolding systems it is important that the processing device has anexcellent temperature time response. The heating element must thereforerapidly and uniformly transfer heat to the body of the processingdevice. Moreover, the connection between the heating element and theprocessing device must be sufficiently firm to withstand the mechanicalforces acting upon the processing device and the heating element duringthe molding process. The same applies to other thermal elements, such asthermocouples, sensors or heating/cooling pipes, regardless of whetherheat is transferred to or from the thermal element.

The above mentioned U.S. Pat. No. 5,051,086 describes a molten materialprocessing device in form of an injection molding nozzle. The device hasan elongated thermal element like a heating element which is wounddirectly around the body of the nozzle. The coils of the heating elementare integrally cast in a nickel-alloy by a brazing step in a vacuumfurnace. The brazing step results in that the nickel-alloy flows intoall of the spaces around the coils thereby metallurgically bonding thecoils to the body of the nozzle. In order to insulate an outer portionof the coils of the heating element which faces to the outside of thenozzle, the coils are covered by plasma sprayed alternating layers ofstainless steel and a ceramic insulating material.

U.S. Pat. No. 4,557,685 proposes an injection molding nozzle having aspiral channel around its cylindrical outer surface. A helical heatingelement is integrally brazed into this channel wherein the brazing takesplace in a vacuum furnace. The solder, in this case a nickel-paste,melts and runs by capillary action into the channel all around theheating element thereby bonding both the heating element and the channeland forming an integral construction.

Both U.S. patents referenced above bond the heating element to the bodyof the nozzle by brazing together both parts in a vacuum furnace.However, the use of such a vacuum furnace is costly and lowers theproduction rate.

U.S. Pat. No. 5,226,596 to Okamura proposes a heated nozzle having aspiral shaped groove on its outer periphery which receives a heatingelement. The groove and the heating element are covered by a metal stripwound around the surface of the outer periphery of the heated nozzlemain body. The metal strip is welded to the nozzle body. However, such aconstruction creates air filled empty spaces between the metal strip andthe heating element thereby partially insulating the surface of theheating element. As a result the temperature of the heating elementundesirably increases in the insulated spots which can destroy theheating element.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a reliable moltenmaterial processing device having an elongated thermal element which canbe produced fast and at reduced costs. It is a further object of theinvention to provide a method which is easy to automate and an apparatusto carry out the method.

It is an advantage of the inventive device that a vacuum furnace is notrequired for its production. Thereby the production rate can beincreased and the production costs can be lowered. Moreover the heattransfer from the heating element to the body of the processing deviceis further improved because both parts are now in direct contact witheach other thereby achieving an optimal effect. Hence the temperaturetime response of the inventive device is further enhanced so thatshorter cycle times are possible.

The inventive method can easily be automated which advantageouslyreduces the production costs. The inventive method further offers thepossibility to use a plurality of different materials with differentmelting points for the thermal spraying. Finally, the heating elementand the processing device are only heated to a small extent in thevicinity of the heating element during the bonding such that nodistortion occurs, which could influence the contact and thus the heattransfer between the heating element and the processing device.

The processing device can be an injection nozzle, a mold manifold, amold gate insert, a nozzle tip, a valve stem, a torpedo, a heater bodyor a sprue bushing. The recess provided in the surface of the processingdevice is preferably a groove.

The first portion of the recess can be a V-shaped opening. Thisconfiguration facilitates and improves the filling of the clear spacebetween the thermal element and the surface of the processing device. Ina preferred embodiment, the opening angle of the first portion is in arange of 30° to 120°.

In another preferred embodiment, the cross-section of the second portionis arcuate such that the cross-section of the second portion is adaptedto the cross-section of a tubular thermal element like a heating elementor a heating/cooling pipe. The angle by which the second portionsurrounds the thermal element is in a preferred embodiment 180° so thata maximum area of the thermal element is in direct contact with theprocessing device. The angle can of course also be smaller than 180°.

Preferably, a groove-like recess is formed in at least one wall of thegroove parallel to the bottom thereof. This groove-like recessadvantageously acts as a spring when pressing the thermal element intothe groove. The groove-like recess can be formed in the first portion ofthe groove. Further, the groove-like recess can be symmetrically formedin opposite walls of the groove.

Preferably, the thermal sprayed material is a heat conductive material.The material can be any of aluminum, bronze, copper, nickel or alloysthereof.

According to a preferred embodiment of the inventive method, the thermalspraying is performed in the form of plasma spraying. Advantageously,initial materials having high melting points can be processed, as thetemperature of the plasma beam is high enough to melt such materials. Inanother preferred embodiment of the inventive method, the thermalspraying can be performed as arc spraying. The advantage of thisembodiment consists in that the initial material can easily be madeavailable in wire form. Finally it is possible to effect the thermalspraying as flame spraying.

Preferably, the surface in which the thermal element is embedded isprocessed to be plane. This can be done by milling, lathing and/orgrounding. In a preferred embodiment the clear space is filled withmaterial by thermally spraying alternating layers onto the thermalelement. Thereby a uniform filling of the clear space is achieved. Theadherence of the thermally sprayed material to the surface of theheating element and to the surface of the recess can be improved bycleaning the surfaces prior to the filling.

BRIEF DESCRIPTION OF THE FIGURES

Following, the invention is explained in more detail by means ofembodiments with regard to the attached drawing wherein shows.

FIG. 1 is a cross-section through a part of an embodiment of theinventive processing device.

FIG. 2 is a cross-section through the part of the embodiment after theheating element was inserted into the recess.

FIG. 3 is a cross-section through the part of the embodiment wherein theclear space is partially filled with thermally sprayed material.

FIG. 4 is a cross-section through the part of the embodiment after theclear space between the surface and the heating element is completelyfilled with thermally sprayed material.

FIG. 5 is a cross-section through the part of the embodiment after thesurface is ground to be plane.

FIG. 6 is a partially enlarged cross-section through another embodimentof the inventive processing device.

FIG. 7 is a cross-section through a further embodiment of the inventiveprocessing device.

FIG. 8 is a cross-section through another embodiment of the inventiveprocessing device.

FIG. 9 is a cross-section through another embodiment of the inventiveprocessing device.

FIG. 10 is a cross-section through another embodiment of the inventiveprocessing device prior to inserting the thermal element.

FIG. 11 is a cross-section through another embodiment of the inventiveprocessing device.

FIG. 12 is a schematic illustration of an apparatus for producing aninventive processing device.

FIG. 13 is an embodiment of the apparatus from FIG. 12.

FIG. 14 is a schematic of a side elevation of an injection moldingmachine partially in cross section.

FIG. 15 is a schematic of a cross sectional top view of an injectionmanifold with a nozzle system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows one part of an embodiment of the processing device 1 whichcan be an injection nozzle, a mold manifold, a mold gate insert, anozzle tip, a sprue bushing, a valve stem, a torpedo and a heater body.This processing device can be used in the molding process of variousmaterials such as plastic resins, metals and powders.

FIG. 1 shows in particular the part of the embodiment of the processingdevice 1 in the area of a recess 3, which is formed in at least onesurface 6 of the processing device 1. Recess 3 extends along the surface6 into the areas of the processing device 1 to be heated. A heating wirecan, for instance, be used as thermal element 2, which is adjusted tothe progress of the recess 3 along the surface 6. Although only onerecess 3 formed in one surface 6 is illustrated in FIG. 1, of course,additional recesses in other surfaces of the processing device 1 can beformed.

In this embodiment, the recess 3 is formed as a groove which is mostsuitable to receive tubular thermal elements such as heating pipes,cooling pipes or heating elements in form of heating wires. The recess 3can have any other form suitable to receive other non-tubular thermalelements. FIG. 1 shows that the recess 3 has a cross-section which islarger than the cross-section of the thermal element 2 shown in FIG. 2.The recess includes a first portion 4 and a second portion 5. The firstportion of the recess realized by this embodiment is a V-shaped openingwhich facilitates the thermal spraying of the material 8 onto thethermal element 2. Moreover, the V-shaped opening also facilitates theinsertion of the thermal element 2 into the recess 3. The second portion5 has an arcuate cross-section which is adapted to the cross-section ofthe thermal element 2. In this case, the second portion 5 surrounds thethermal element by the maximal possible angle of 180°. Any other anglewhich is less than 180° is also possible.

Furthermore it can be seen from FIG. 1 that two groove-like recesses 9are formed in the walls of the recess 3. The groove-like recesses 9extend parallel to the bottom of the recess 3 and act as a spring whenthe thermal element 2 is pressed into the recess 3 during the mountingof the element 2. In this embodiment, the groove-like recesses 9 aresymmetrically arranged in opposite walls of the first portion of therecess 3. Other arrangements for example with only one groove-likerecess 9 are likewise possible.

According to FIG. 2 the thermal element 2 is inserted into the recess 3.It can be seen in FIG. 2 that by inserting the thermal element 2 intothe recess 3, a clear space 7 is formed between the surface 6 of theprocessing device 1 and the thermal element 2. By means of the V-shapedopening of recess 3, the clear space 7 is expanded towards the surface 6such that the thermal element 2 is well accessible. Thus, spraying thematerial 8 onto the thermal element 2 is facilitated.

FIG. 3 illustrates the clear space 7 partially filled with material 8 bythermal spraying. Hot particles of the material 8 are acceleratedtowards the clear space 7, which particles impact at high speed on thefree surface, i.e., the surface of the thermal element 2 facing theclear space 7. Thus, the material 8 is sprayed onto the thermal element2 until the clear space 7 is filled. The hot particles are not shown inFIG. 3. Advantageously, the material 8 is sprayed on the thermal element2 layer by layer such that the clear space 7 is filled uniformly. Thematerial 8 thereby solidifies to form a layer completely covering thethermal element 2, onto which additional layers are sprayed one by oneuntil the clear space 7 is completely filled. The V-shaped opening ofthe recess 3 allows a larger amount of material 8 to reach the clearspace 7 in order to be deposited on the heating element.

FIG. 4 illustrates a clear space 7 completely filled with thermallysprayed material 8. The solidified layers sprayed onto the thermalelement 2 adhere to both the free surface of thermal element 2 and tothe wall of the V-shaped opening 7 of recess 3. The thermal element 2 isthereby fixed in the recess 3 such that the required solid compound andthe required good heat transmission between the processing device 1 andthe thermal element 2 are guaranteed. In order to improve the adherenceof the solidified thermally sprayed material 8 on the thermal element 2and on the walls of the recess 3, the surfaces of the thermal element 2and the wall contacting the material 8 can be cleaned prior to spraying.The cleaning can, for instance, be effected by means of sand blasting.

Although it has shown that the layer-wise filling of the clear space 7entails excellent results, other ways of proceeding for the filling arepossible. After filling the clear space 7, the surface 6 of theprocessing device 1 is processed to be plane, then having the form as itis shown in FIG. 5.

A heating wire can be used as heating element, the core of which isformed by a heat conductor. The heat conductor being current-carryingduring the heating operation is enclosed by an insulating layer, whichagain is enclosed by a tubular heating element. The tubular heatingelement forms the upper surface of the thermal element 2, onto which thehot particles are sprayed at high speed. The tubular heating elementcan, for instance, be made of steel.

Other elements can be used as the elongated thermal element 2 such as asensor, a thermocouple, a heating pipe and a cooling pipe.

The embodiment illustrated in FIG. 6 is an injection mold nozzle havinga heated insert as processing device 1. The heated insert includes arecess 3 in its outer surface having a first portion 4 and a secondportion 5. Recess 3 receives a heating element 2. The clear space 7between the heating element and the surface 6 is filled with thethermally sprayed material 8. For this embodiment it is important thatthe surface 6 is processed to be plane so that the processing device 1can be inserted into the nozzle. FIG. 7 shows a heated bushing asprocessing device 1 which can be mounted on an injection mold nozzleaccording to FIG. 8. In FIG. 9, the processing device is a mold manifoldhaving an upper plate 11 comprising the embedded heating element 2. Meltchannels 10 are provided in a lower plate 12. The course of the recess 3and hence of the heating element 2 in the upper plate 11 corresponds tothe course of the melt channel 10 in the lower plate 12. FIG. 10 showsan injection nozzle having a spiral shaped groove as recess 3 in itsouter surface 6. This nozzle is shown prior to inserting the heatingelement 2 into the groove. FIG. 11 illustrates an injection nozzle 1having a heating element 2 which runs substantially longitudinal to thenozzle 1.

From the above it is clear that the invention can be realized ondifferent types of processing devices 1. Furthermore the inventionallows elongated thermal elements to be embedded regardless of thelongitudinal form of the elongated thermal element 2.

FIGS. 1-5 illustrate the steps of producing a molten material processingdevice 1 having an elongated thermal element 2. A molten materialprocessing device 1 having a recess 3 in a surface 6 thereof is providedin FIG. 1. The recess 3 has a cross-section, which is larger than across-section of the thermal element 2. Further the recess 3 includes afirst portion 4 and a second portion 5 which has a shape correspondingpartially to a cross-section of the thermal element 2. The recess 3 canbe formed by milling. FIG. 2 shows the step of inserting and pressingthe thermal element 2 into the second portion 5 so as to form betweenthe thermal element 2 and the surface 6 of the processing device 1 aclear space 7 limited by the first portion 4 and the thermal element 2.By pressing the thermal element 2 into the recess 3 during its insertiona desired uniform contact between the wall of recess 3 and the thermalelement 2 is achieved. In FIGS. 3 and 4 it is seen how the clear space 7is filled with material 8 by thermal spraying thereby embedding thethermal element 2 in the processing device 1.

The filling of the clear space 7 is carried out by thermal spraying. Aninitial material, which can be metallic, is thereby molten, atomized andaccelerated, and sprayed on the heating element in the form of particlesuntil the clear space 7 is filled. The advantage of this process stepconsists particularly in that the hot particles stick to the wall of therecess when filling the clear space, such that upon solidification ofthe layer consisting of the particles covering the heating element, theheating element is firmly fixed in the recess.

The thermal spraying process can be carried out in the form of plasmaspraying, flame spraying or arc spraying.

In case of plasma spraying, the initial material is introduced into aplasma beam in a powdery form, which beam melts the powder andaccelerates it towards the clear space 7. The so formed hot andaccelerated particles are thereby sprayed onto the thermal element 2until the clear space 7 is filled. For producing the plasma beam, an arcis ignited between two non-melting electrodes, to which arc astabilizing gas is added. The added stabilizing gas, such as N₂, N₂+≦10%H₂, Ar, He or Ar+N₂ is ionized to form plasma, which exits at high speedfrom a nozzle in the form of a beam. By means of a carrier gas thepowder is blown into the plasma beam, which is molten and cast onto thefree surface of the thermal element 2. In this way the heating elementcan be sprayed on until the clear space 7 is completely filled. In orderto obtain a filling as uniform as possible, the particles can be sprayedonto the heating element layer by layer. Due to the high temperature ofthe plasma beam, most metallic powders, but also other suitable powderscan be applied.

In the case of arc spraying the initial material is in wire form. Forproducing the hot accelerated particles, two electrodes made from theinitial material are contacted. After the ignition an arc is formedbetween the two wires, whereupon the two wires continuously melt. Themolten mass is atomized, accelerated and blown onto the free surface ofthe heating element by means of a current of compressed air. In thisway, the heating element can be sprayed on until the clear space 7 iscompletely filled. In order to obtain a filling as uniform as possible,here too, the particles can sprayed onto the thermal element 2 layer bylayer.

As shown in FIG. 5, the surface 6 in which the thermal element isembedded can be processed to be plane for example by milling, lathingand/or grinding.

Aluminum, bronze, copper or nickel have been approved of as initialmaterial.

FIG. 12 shows an embodiment of an apparatus for producing a moltenmaterial processing device 1 having an elongated thermal element 2. Thisapparatus includes thermal spraying equipment 100 consisting for exampleof a plasma gun. This equipment 100 is movably arranged. Further, thisapparatus includes a supporting device 110 for supporting the processingdevice 1 and a pressing device (not shown in FIG. 12). The pressingdevice presses the thermal element 2 into the recess 3 in order tomaintain a tight contact between the thermal element 2 and theprocessing device 1 during the thermal spraying. A control device 130controls the supporting device 110 as well as a driving mechanism 140which moves the thermal spraying equipment 100.

FIG. 13 shows another embodiment of the apparatus in which two plasmaguns are provided which each can spray another material onto the thermalelement 2. A first material could for example improve the adhesion of asecond thermal conductive material on the thermal element 2.

FIG. 14 shows a schematic illustration of an injection molding machinewherein the embodiments of the processing device described above can beincorporated.

The injection molding machine includes an injection molding extruder 20,which provides for the molding resin as well as a stationary mold half21 and a movable mold half 22, which is movable with respect to thestationary mold half 21. The stationary mold half 21 and the movablemold half 22 are held in a support frame. The injection molding extruder20 is controlled by an extruder controller 23. Arranged within thestationary mold half 21 are hot runner injection nozzles 24, which canbe constructed as described above in view of the processing device 1. Atone end of the hot runner injection nozzle 24 is located the mold gate25 which leads to the mold cavity 26.

The movable mold half 22 is provided with mold cores 27, which can beinserted into the mold cavities 26.

Especially to control the heat within the hot runner system of thestationary mold half 21, a hot runner controller 28 is provided which isconnected through a lead 29 to the stationary mold half 21.

Turning now to FIG. 15, the injection manifold with the nozzle system isshown in more detail.

A sprue bushing 30 is provided to inject molding resin from the extruder20 into the mold manifold 31. Embedded within the mold manifold 31 aremanifold heaters 32 to keep the temperature within the manifold 31 inthe desired temperature range. The channel coming from the sprue bushing30 is divided into two manifold melt channels 33. The melt channel 33leads to hot runner nozzle 34 and extends there through to a mold gate35. Within the mold cavity 36 is located a mold core 37.

A valve pin 38 extends all through a part of the melt channel 33 and isactuated by a valve pin actuator 39 on the rear side of the moldmanifold 31.

The hot runner nozzle 34 includes a nozzle tip and seal assembly 40 toseal the melt channel 33 with respect to the gate 35. Around the area ofthe gate is arranged a gate cooling channel 41.

The hot runner nozzle 34 is heated by a nozzle heater 42 which isarranged around the circumference of the nozzle 34.

As already indicated above, the injection molding machine shown in FIG.14 and the injection manifold with a nozzle system shown in FIG. 15 canincorporate a processing device which can be the injection nozzle, themold manifold, the mold gate insert, the nozzle tip, a sprue bushing, avalve stem, a torpedo or a heater body, which can be of the structure asdescribed in the embodiments above and which can be manufactured by themethod also described above.

1. A method of manufacturing an injection molding hot runner nozzleusing a thermal spraying apparatus comprising: providing a hot runnernozzle body having a nozzle melt channel and a nozzle outer surface;placing said nozzle body on a supporting device associated with thethermal spraying apparatus, where said supporting device is furthercapable of rotating said nozzle body; applying a first layered materialhaving metallic characteristics onto said nozzle body using a sprayinggun associated with a thermal spraying apparatus, wherein said layeredmaterial is sprayed while rotating said nozzle body; and providing aprocessor that controls the relative position between the nozzle bodyretained by the supporting device and the spraying gun.
 2. The method ofmanufacturing an injection molding hot runner nozzle according to claim1, wherein said applying of the first layered material is carried out bya thermal spraying process selected from a group consisting of plasmaspraying, flame spraying and arc spraying.
 3. The method ofmanufacturing an injection molding hot runner nozzle according to claim1, wherein the first layered material includes one of aluminum, bronze,copper and nickel.
 4. The method of manufacturing an injection moldinghot runner nozzle according to claim 1, wherein the first layeredmaterial is a thermally conductive material.
 5. The method ofmanufacturing an injection molding hot runner nozzle according to claim1, wherein a second layered material is sprayed onto said outer surfaceof said nozzle body.
 6. The method of manufacturing an injection moldinghot runner nozzle according to claim 5, wherein the second layeredmaterial has adhesive characteristics.
 7. The method of manufacturing aninjection molding hot runner nozzle according to claim 1, wherein thefirst layered material is applied onto select portions of said outersurface of said nozzle body.
 8. The method of manufacturing an injectionmolding hot runner nozzle according to claim 1, further comprising:performing a cleaning process on said outer surface of said nozzle bodyprior to applying the first layer material.
 9. The method ofmanufacturing an injection molding hot runner nozzle according to claim8, wherein said cleaning process includes sand blasting said outersurface of said nozzle body.